The aspiration of fluids from a patient is accomplished by providing a vacuum source through a catheter to the internal body area of the patient requiring aspiration. Typically, unregulated hospital vacuum line pressure is approximately between 19" to 25" of mercury (Hg.).
The use of vacuum regulators as medical devices is well known to achieve such aspiration of fluids. Generally such vacuum regulators are attached to a vacuum outlet in the wall of the patient's hospital room. Known vacuum suction regulators include a variable vacuum regulator, the vacuum gauge and a mechanical mechanism which cycles the vacuum on and off at predetermined timed intervals. Certain of these vacuum regulators are mechanical devices which use the vacuum source as a means of powering the cycling mechanism. Through practice it has been determined that a preferred off and on cycle is at such ratio that the vacuum regulator will be effective for twice the time that it is on as compared with the time that it is off. This two to one ratio is the ratio usually employed in currently available vacuum regulators even where this ratio can be varied as in an available intermittent vacuum regulators such as the one marketed under the name Vacutron sold by Allied Healthcare Products, Inc. of St. Louis, Mo.
Such known mechanical intermittent vacuum regulators achieve vacuum cycling by means of precise air flow into and out of an air chamber. In the Vacutron intermittent regulator there is a spring loaded mechanism in combination with a diaphragm assembly that controls the rotating valve. This mechanism is rather large and is not modular, i.e., failure of any of the springs, clevis arms, diaphragm, etc. requires the disassembly of the entire mechanism. A field service representative would either have to be called out or the faulty unit returned to the manufacturer for repair. Such a device allows the volume in the chamber to increase and decrease on a periodic basis. The diaphragm will be connected to a mechanism that cycles to the vacuum on and off. In order to control the on/off time periods two needle valves control the air flow into and out of the diaphragm. Problems arise with such known devices due to the fact that the on/off time periods are fairly long and the total air chamber volume is quite small. Therefore, in order to operate at such small flow rates, the valve openings themselves are also small. The small valve openings make the timing of the intermittent regulator sensitive to clogging by means of small dirt particles in the vacuum line.
There are other types of known mechanical intermediate vacuum regulators which utilize vacuum as a means to power the regulators. However, they are operated by a pneumatic logic type system. Such devices are also subject to becoming clogged by means of small dirt particles.